Right so as whil that Iren is hoot men sholden smyte. [Chaucer, c.1386]

Chemical symbol Fe is from the Latin word for the metal, ferrum (see ferro-). Meaning "metal device used to press or smooth clothes" is from 1610s. The adjective is Old English iren, isern. To have (too) many irons in the fire "to be doing too much at once" is from 1540s. Iron lung "artificial respiration tank" is from 1932.

v.

c.1400, irenen, "to make of iron," from iron (n.). Meaning "press clothes" (with a heated flat-iron) is recorded from 1670s. Related: Ironed; ironing.

(ī'ərn) Symbol FeA silvery-white, hard metallic element that occurs abundantly in minerals such as hematite, magnetite, pyrite, and ilmenite. It is malleable and ductile, can be magnetized, and rusts readily in moist air. It is used to make steel and other alloys important in construction and manufacturing. Iron is a component of hemoglobin, which allows red blood cells to carry oxygen and carbon dioxide through the body. Atomic number 26; atomic weight 55.845; melting point 1,535°C; boiling point 2,750°C; specific gravity 7.874 (at 20°C); valence 2, 3, 4, 6. See Periodic Table. See Note at element.

iron out

Work out, resolve, settle. For example, They managed to iron out all the problems with the new production process, or John and Mary finally ironed out their differences. This expression uses ironing wrinkled fabric as a metaphor for smoothing differences.
[ Mid-1800s
]